[프로그래머스] 조건에 부합하는 중고거래 댓글 조회하기

SELECT
    gb.TITLE,
    gb.BOARD_ID,
    gr.REPLY_ID,
    gr.WRITER_ID,
    gr.CONTENTS,
    DATE_FORMAT(gr.CREATED_DATE, '%Y-%m-%d') AS CREATED_DATE
FROM USED_GOODS_BOARD AS gb
JOIN USED_GOODS_REPLY AS gr
    ON gb.BOARD_ID = gr.BOARD_ID
WHERE YEAR(gb.CREATED_DATE) = 2022
    AND MONTH(gb.CREATED_DATE) = 10
ORDER BY gr.CREATED_DATE, gb.TITLE

• USED_GOODS_BOARDS 쪽으로 inner join
• 댓글이 아닌 게시물의 생성 시점이 조건이므로 where절에서 USER_GOODS_BOARDS 테이블을 참조
• DATE_FORMAT(gr.CREATED_DATE, '%Y-%m') = '2022-10'보다 YEAR(gb.CREATED_DATE) = 2022 AND MONTH(gb.CREATED_DATE) = 10이 성능면에서 낫다함.